Polishing substrates is becoming increasingly more common as semiconductor devices continue to shrink. In order to polish in a production environment, the polishing process needs to be characterized and controlled. Generally, film removal rate variations are more frequent with metal polishing processes. Variations are also observed with other post-polishing parameters including planarity, dishing erosion, recess, or the like. Sources of film removal rate variation include unstable tool parameters, degradation of the polishing pad, and variation in slurry properties.
Selectivity between the metal layer and an underlying insulating layer is typically achieved using alumina-based slurries. Alumina is typically a crystalline material that can have several crystallographic phases including alpha, beta, gamma, and delta phases. Bulk materials of each phase can exhibit different mechanical and sur face chemistry properties. FIG. 1 includes an illustration of a particle 10 within a slurry solution. The particle 10 has positive surface charges 12 that are countered by negative ions 14 within the solution. The zeta potential is the potential at the slippage plane 16 and may be positive or negative. Currently, some of the slurry properties monitored in semiconductor manufacturing include pH, solid content particle size, conductivity, and zeta potential. The prior art has been unsuccessful in providing a reliable correlation between the properties of the slurry abrasive materials and performance of the planarization processes.